1. Field of the Invention
This invention relates to a stabilized hydroxylamine solution, and more particularly, to a hydroxylamine solution, which comprises a selected stabilizer.
2. Description of the Related Art
Hydroxylamine, especially in the form of its salts with sulfuric acid, hydrochloric acid and others, is an important intermediate for the chemical industry, and is widely employed in chemical syntheses. It is frequently necessary to employ hydroxylamine in the form of a solution of the free base, which is generally liberated from a hydroxylammonium salt such as, for example, hydroxylammonium sulfate or hydroxylammonium chloride, by the action of an appropriate base, such as ammonia, sodium hydroxide solution or an alcoholate. Neutral and alkaline hdyroxylamine solutions are unstable and decompose to form ammonia, nitrogen, oxides of nitrogen and water, so that their transportation or storage is highly problematic. The rate of decomposition increases with rising temperature, rising hydroxylamine concentration, rising pH and rising concentration of catalytically active impurities.
In Order to avoid the decomposition of the hydroxylamine, a stabilizer is added to the solutions. Numerous stabilizers for hydroxylamine are already known. Proposals which have been made are: thioglycolic acid (JP-A-58069843), glycerol monethers and ethylene oxide adducts thereof (DE-A-29 19 554), hydroxyanthraquinones (DE-A-33 43 600), hydroxyquinolines (DE-A-33 45 734), polyhydroxyhexano-1,4-lactone (DE-A-33 45 733), anthocyanins (DE-A-33 47 260), hydroxyquinaldines, flavones, benzonitrile, N-phenyl-N hydroxythiourea (DE-A-36 01 803), flavans (DE-A-33 43 599), thiosulfates, mercaptobenzothiazoles, mercaptoalkanols, mercaptothiazolines, thiuram disulfides, thioureas (EP-A-516 933), the tetrasodium salt of ethylenediaminetetraacetic acid, the trisodium salt of N-hydroxyethylenediaminetriacetic acid, polyvinylpyrrolidone or poly-N-vinyl-5-ethyl-2-oxazolidinone (U.S. Pat. No. 3,145,082), amide oximes (U.S. Pat. No. 3,480,391), hydroxamic acids (U.S. Pat. No. 3,480,391), hydroxyureas (U.S. Pat. No. 3,544,270), dipyridyl compounds (JP-A-58069842), aminoquinolines (JP-A-58069844), phenanthrolines (JP A-58069841), and polyhydroxyphenols (JP-A-4878099).
However, none of the stabilizers proposed to date has been able to provide hydroxylamine solutions with sufficient stabilization to prevent excessive decomposition of the hydroxylamine to occur, especially during storage.
What is desired and needed is a better means for stabilizing a hydroxylamine solution.